Structure and Magnetic Properties of PrCo_5-based Magnets Prepared by Mechanical Alloying

摘要

The Pr_xCo_(100-x) (x = 14 - 22) alloy powders have been prepared by mechanical alloying and subsequent annealing. Structure and magnetic properties of the alloys have been investigated systematically. The analyses of XRD patterns and M-T curves reveal that the main phase is Pr_2Co_(17) with rhombohedral Th_2Zn_(17)-type for x = 14. The amount of the Pr_2Co_(17) phase decreases with increasing Pr content, and a nearly single phase PrCo_5 with hexagonal CaCu_5-type is formed in Pr_(19)Co_(81) powders. Further increasing the Pr content leads to the formation of another magnetically hard Pr_2Co_7 phase with its Curie temperature about 350℃. Remanences decrease monotonously with increasing Pr content, whereas the coercivities increase, reaching a maximum of 20.4 kA/cm (25.5 kOe) in Pr_(19)Co_(81) powders milled for 5 h and annealed at 700℃ for 2 mm, and then decrease for higher Pr content. The high coercivity originates from the high anisotropic field of the PrCo_5 phase.